With the increase in environmental oversight, operators of power plants are pushing to discover new and better ways to remediate potential pollutants which are the byproducts of the power generation process. A variety of approaches have been developed for removal or mitigation of such byproducts resulting from coal fired power plants. One known approach is the use of dry sorbent injection (DSI) systems to reduce acid gas levels, such as sulfur dioxide (SO2), sulfur trioxide (SO3), sulfuric acid (H2SO4), and hydrochloric acid (HCl). DSI involves the addition of an alkaline material (such as sodium bicarbonate, hydrated lime, or trona) into various locations of the power plant system such that the acid gases react with the alkaline sorbents to form solid salts which are removed via a particulate control device.
While DSI is a cost effective control solution, it is not without its own processing challenges. For instance, certain sorbent materials are prone to clumping or agglomeration, while some sorbent materials (e.g., trona) are known to require milling in order to increase the surface area for reaction and to be more cost effective. For a variety of reasons (e.g., superior flow properties and predictability of particulate size), the use of on-site milling for certain sorbent particulate is preferred. One particularly effective method of on-site milling is the use of an in-line pneumatic milling system, which provides a superior reduction of SO2 or SO3 stack emissions when injecting trona or sodium bicarbonate. This approach, however, creates problems in that the consistent injection of the pressurized fluid in an inlet port can create concentrated and uneven wear or material buildup on the rotor and cutting surfaces of the mill. Such wear/buildup, in turn, can precipitate premature replacement or failure of the mill, as well as reducing the efficacy of the milling process, with the consequential degrading of the efficacy of the contaminant remediation process.
Thus, the present state of the art reflects a need for a system which reliably mills entrained particulate entrained in a pressurized fluid (such as sorbent particulate in a pneumatic conveyance system) in an inline mill configuration without creating undue wear or buildup on mill rotors and cutting surfaces, as such wear may increase maintenance costs and failure risks and decrease the efficacy of the system.